http://www.perlmonks.org?node_id=803642


in reply to Re: Random numbers are not random enough on Windows
in thread Random numbers are not random enough on Windows

$ perl -V:randbits

On my Ubuntu box this prints randbits='48';  On your build of Perl I suspect it's 15.

(This value is figured out at build-time and is supposed to represent how many bits the respective PRNG C library function actually provides.)